Research teams in the United States, Britain, Canada, Iceland, Norway, and Sweden have worked in close coordination to create the North Atlantic Population Project (NAPP), a massive integrated cross-national microdatabase that provides a baseline for studies of demographic change and opens fresh paths for spatiotemporal data analysis. We now propose improvements that will multiply the power of the NAPP infrastructure. We have three major aims: (1) Triple the size of the database to approximately 365 million records, adding 40 new datasets for the period 1787 to 1930 from Albania, Britain, Canada, Denmark, Egypt, Iceland, Ireland, Germany, Norway, Mexico, Sweden, and the United States. (2) Leverage our innovative record-linkage technology to create linked national panels that will allow expanded longitudinal analyses. (3) Connect the past to the present by merging NAPP with the Integrated Public Use Microdata Series (IPUMS), simplifying analysis of long-run change and ensuring long-run preservation and maintenance of the database. The landscape of scientific research on the human population is shifting. It is no longer sufficient just to study the relationships among variables at a particular moment in time. Researchers around the world now recognize that to understand the large-scale processes that are transforming society, we must investigate long-term change. The goal of this project is to provide the infrastructure to make such analysis possible. NAPP will make a strategic contribution to demographic infrastructure by providing a baseline for the study of changes in the demography and health of European and North American populations. In each country, NAPP provides the earliest census microdata available. Models and descriptions based on historical experience underlie both theories of past change and projections into the future. The NAPP data provide a unique laboratory for the study of economic and demographic processes; this kind of empirical foundation is essential for testing social and economic theory. The proposed work will be carried out by a team of highly-skilled researchers with unparalleled expertise and experience in data integration and record linkage. Collaborators include leading researchers from the University of Minnesota and the Max Planck Institute for Demographic Research, and local experts from each of the participating countries. Centralized support for international collaboration will leverage the investments of each country and allow us to create an extraordinary resource for comparative social and economic research.